There's no way to be completely prepared for a movie like "The Opposite of Sex."

For example, with its themes of blackmail, illicit sexual relations and violent death you'd expect the film to be a thriller. Instead, it's a caustic comedy that benefits from some unlikely moviemaking decisions.Probably the most unlikely of these is casting former child star Christina Ricci as its main character, a potty-mouthed, chain-smoking 16-year-old sexpot named Dedee Truitt.

Dedee also serves as the movie's wisecracking narrator, who serves up biting commentary as she prepares to wreck the lives of several Indiana residents. Foremost among them is Bill Truitt (indie actor Martin Donovan), her much-older half-brother.

Having already run away from Louisiana, Dedee turns up on Bill's doorstep and proceeds to seduce his live-in lover, Matt (Ivan Sergei). A month later, she claims to be pregnant with Matt's child and, with the naive man in tow, flees to California.

Needless to say, that leaves the clueless Bill, as well as his faithful friend and co-worker Lucia (Lisa Kudrow, from TV's "Friends"), speechless. Further complicating Bill's life are allegations from a former student (Johnny Galecki) who claims he sexually molested him.

On top of some great performances, especially from Ricci and Donovan, the movie features a clever, top-notch script from first-time director Don Roos (who also wrote the recent remake of "Diabolique"). His direction is more problematic - including some technical deficiencies - but the irreverently humorous tone more than makes up for it.

And though Ricci's deadpan voice-over is definitely one of the film's biggest assets, there's also an unlikely but charming romance between Kudrow's character and a police officer (Lyle Lovett) that almost steals the show.

"The Opposite of Sex" is rated R for profanity, violent fist fighting and gunplay, simulated sex, use of vulgar slang terms and some sex talk, nude drawings and a briefly gory birthing scene.